Temporary, external ventricular drainage (ventriculostomy) catheters are utilized in the treatment of hydrocephalus and intracranial hypertension, when the use of a permanent internal shunting system is not indicated i.e. when the problem is expected to resolve. The catheter is inserted via an incision made in the scalp skin and through a hole drilled in the underlying skull bone. The catheter is passed through the brain substance and into the ventricles which are the chambers deep within the brain that contain the cerebrospinal fluid (CSF).
The catheter allows for the monitoring of the intracranial pressure and also for the drainage of CSF, as necessary, to lower the intracranial pressure.
The use of a rubber catheter inserted percutaneously into the cerebral ventricles for the drainage of unwanted CSF was first described in 1943. (Crawford AS, Munslow RA: Annals of Surgery 117:798-799, 1943) Since that time, one of the major persisting risks associated with percutaneous ventricular drainage catheters has been infection of the brain or CSF. The catheter provides an open pathway for the migration of bacteria along the catheter and into the brain. A resulting infection (meningitis or ventriculitis), which has been reported to occur in up to 27% of patients with ventricular drainage catheters in place, may be life-threatening. (Mayhall CG, et al: New England Journal of Medicine 310:553-559, 1984) Because of this, many avenues have been explored to reduce the risk of ventricular drain infections.
Some neurosurgeons administer prophylactic antibiotics at the time of insertion of a ventricular drainage catheter and for as long as it remains in place. Nevertheless, the only study demonstrating a relative reduction in the rate of infection with the use of prophylactic antibiotics still reported an unacceptably high rate of infection (9%) in patients with ventricular drainage catheters. (Wyler AR, Kelly WA: Journal of Neurosurgery 37:185-187, 1972) Furthermore, many authorities suggest that this practice results in the selection of more virulent organisms that are resistant to the usual antibiotic agents thereby making any infection that does occur more dangerous and more difficult to treat. The routine use of prophylactic antibiotics for ventricular drainage catheters therefore remains controversial. (Stenager E, et al: Acta Neurochirurgica 83:20-23, 1986)
In many institutions, protocols have been established requiring that ventriculostomy catheters be changed to a new site every five to seven days, in an attempt to reduce infection by bacteria that colonize the catheter and migrate along its outer surface into the brain. (Mayhall CG, et al: New England Journal of Medicine 310:553-559, 1984) This requires a new scalp incision, a new hole drilled in the skull, and the passage of another catheter through the brain substance. This practice has not been clearly proven to reduce infection rates, and it also carries other risks, especially for those patients requiring external ventricular drainage for several weeks who may undergo four or five ventriculostomy changes. (Kanter RK, Weiner LB: New England Journal of Medicine 311:987, 1984) Each time a new catheter is placed, there is a new risk of injuring brain tissue and of causing dangerous bleeding by disrupting an artery or vein. Additionally, there is a new chance of introducing infection into the brain with each new passage of a foreign body.
Ideally, all ventricular drainage catheters are inserted under strict, sterile conditions such as in an operating room or in an intensive care unit setting. But in emergency situations, the catheter may have to be inserted under suboptimal conditions, for example in an emergency room. No matter how much precaution is exercised, the end result is still a percutaneous catheter that establishes a connection between an unsterile outside environment and the brain. This is simply an invitation for infection, and further measures to limit such infections are clearly necessary.
All temporary, external ventricular drainage catheter systems currently in use suffer from a number of disadvantages:
(a) The catheters pose a serious risk of infection to the brain and cerebrospinal fluid as bacteria can migrate along the open tract, around the catheters, as detailed above;
(b) The catheters are routinely changed approximately every five days which increases the chance of injuring the brain tissue or cerebral blood vessels, especially for patients who may require ventricular drainage for prolonged periods of time and thus require multiple catheter changes;
(c) The catheter is free at its entrance to the skull and may thus migrate inward, possibly injuring underlying brain tissue, or outward, possibly requiring its replacement and further increasing the risk of infection or injury;
(d) There is a free open space in the skull hole around the catheter and thus CSF may leak out around the catheter, invalidating measurements of intracranial pressure, and establishing a direct stream of CSF which connects the cerebral ventricles with the unsterile scalp and provides a patent conduit for migration of bacteria;
(e) A chronic leakage of CSF may develop after the catheter is removed, possibly necessitating further repair measures, as the hole drilled in the skull is left unsealed;
(f) A skull defect is left by the open drill hole once the catheter is removed.